OpenTherm Compatibility List
The Therma One T1 supports the OpenTherm protocol (v2.2 and later) for modulating boiler control. When connected via OpenTherm, the T1 can adjust the boiler's flow temperature dynamically rather than using simple on/off relay switching, resulting in improved energy efficiency and more stable room temperatures.
The table below lists boilers and heat pumps that have been tested with the T1. "Verified" means the combination has been tested in our lab. "Community tested" means installers or users have reported successful operation but the pairing has not been formally lab-verified.
Compatible boilers
| Brand | Model | Protocol | Status |
|---|---|---|---|
| HeatPro | Eco 30 | OT v2.2 | Verified |
| HeatPro | Eco 45 | OT v2.2 | Verified |
| FlowMax | Combi 28 | OT v3.0 | Verified |
| FlowMax | Combi 35 | OT v3.0 | Verified |
| Brennley | iSystem 24 | OT v2.2 | Verified |
| Caldero | Prime 30C | OT v2.2 | Community tested |
| Thermalink | EcoElite 25 | OT v3.0 | Verified |
| Thermalink | EcoElite 32 | OT v3.0 | Community tested |
| Nordvik | Compact 28S | OT v2.2 | Verified |
| Solaris | MaxHeat 40 | OT v2.2 | Community tested |
Heat pump compatibility
The T1 also supports OpenTherm communication with air-source and ground-source heat pumps. Heat pump mode enables lower flow temperature targets and longer cycle times suited to heat pump operation.
| Brand | Model | Protocol | Status |
|---|---|---|---|
| AeroWarm | AirSource 8 | OT v3.0 | Verified |
| AeroWarm | AirSource 12 | OT v3.0 | Verified |
| GeoTherm | GroundPro 6 | OT v2.2 | Community tested |
Note: When using the T1 with a heat pump, enable Heat Pump Mode at Settings > Installer > System Type > Heat Pump. This adjusts the control algorithm for slower response times and prevents short-cycling. Maximum flow temperature should typically be set to 45°C for underfloor heating or 55°C for radiators.
Not on the list?
If your boiler or heat pump is not listed above, it may still work with the T1 if it has OpenTherm terminals. The T1 will attempt to negotiate an OpenTherm connection at startup. If negotiation fails, the T1 falls back to relay (on/off) control automatically.
To report a successful pairing with an unlisted boiler, email compatibility@monverta.com with the boiler brand, model number, and OpenTherm firmware version (found in the boiler's service menu). We update this list quarterly.